Hydrocephalus itself is not especially difficult to diagnose, although it may require referral by the general practitioner to a specialized referral clinic or veterinary teaching hospital that has the appropriate diagnostic instruments. The dog’s presenting signs usually prompt a thorough neurological examination, after a history is taken from the owner and a routine physical examination is performed. Most veterinarians will take urine and blood samples as part of the initial data base. However, if hydrocephalus is the dog’s only problem and it is not caused by infection or some other systemic disease, the results of those tests will usually be normal. Radiographs (X-rays) of the dog’s skull may be advised; these may reflect anatomical changes associated with hydrocephalus.
Advanced testing is often necessary to reach a definitive diagnosis of hydrocephalus. This can include ultrasonography, computed tomography (CT scan) and/or magnetic resonance imaging (MRI) of the brain and skull. Another confirmatory technique called electroencephalography may also help with the diagnosis, especially of congenital hydrocephalus.
The veterinarian may recommend evaluating the dog’s cerebrospinal fluid (CSF), depending upon the circumstances of the particular case. CSF analysis requires that the dog be put under general anesthesia. The sample typically is taken from the back of the neck, where the spine meets the skull. The veterinarian will very carefully insert a sterile spinal needle perpendicular to the dog’s skin until it enters what is called the “subarachnoid space.” Once that happens, the CSF will flow freely out through the needle into a special collection tube, for submission to a veterinary pathology laboratory. Special care must be taken when sampling CSF from a dog with hydrocephalus because of the elevated intracranial pressure that usually accompanies the condition. Inserting a spinal needle into the subarachnoid space will suddenly create a passageway through which the accumulated cerebrospinal fluid may be able to exit. This can cause the brain to herniate out through that opening, which can be fatal.
Dogs with hydrocephalus that have a swift onset of neurological signs and are obviously deteriorating rapidly require immediate veterinary intervention. This should be considered to be a true medical emergency. Care must be taken not to over-hydrate dogs with hydrocephalus through aggressive intravenous or subcutaneous fluid therapy, to avoid accelerating the increase in pressure inside the skull.